1. Field of the Invention
The invention relates to an antenna with an omni-directional antenna and with a (first) auxiliary antenna, the received signals of which are combined in respect of amplitude and phase in such a way that a reception minimum results in a desired spatial direction.
2. Discussion of Background
Such an arrangement with two electrically connected antennae and a single reception minimum is known from EP 0 124 047 A2. The reception minimum serves to attenuate the signals from a jammer (jamming transmitter) which is interfering with reception by the antenna installation, sufficiently so that useful signals can be received from a direction other than that of the jammer.
Omni-directional antennae particularly with an almost hemispherical receiving range are well suited for the receipt of signals transmitted from satellites, in particular from satellites traversing the earth's surface. These include, for example, location and navigation satellites, e.g. GPS satellites (GPS=Global Positioning System). It can be assumed that the jamming capacity of the jammer is greater or even very much greater than the capacity of the individual satellites to be received at a ground station. Known modern GPS receivers, certainly tolerate interference levels up to a certain extent greater than the GPS receiving capacity. However, where the interfering capacity is too great, a reduction of the interfering capacity is required.
The use of an omni-directional antenna with a single auxiliary antenna for the production of a single reception minimum produces a funnel shaped reception minimum and not a point reception minimum. The effect of this is that with sufficiently strong suppression of the jamming, reception of a satellite cannot be recieved with suffiecient strength, not only when it is exactly in the same direction as the interference, but also when it is in a spatial angular region in the vicinity of the jammer, due to the strong attenuation of the reception signal.